Aldehyde-functionalized polymers based on polyacrylamide (and similar polymers as described herein), provide a multitude of benefits for paper and paperboard manufacturing that include temporary wet strength, dry strength, wet-web strength, Yankee dryer adhesives, and increased press dewatering. Such polymers are most commonly used in the paper and paperboard industry as additives to provide temporary wet strength and dry strength (see e.g., Coscia et al. U.S. Pat. No. 3,556,932, “Water-Soluble, Ionic, Glyoxalated, Vinylamide, Wet-Strength Resing and Paper Made Therewith”; Farley, C. E., “Glyoxalated Polyacrylamide Resin, pp. 45-61, in Wet-Strength Resins and Their Application, TAPPI Press: Atlanta, Ga., 1994). More recent innovations in these types of polymers are disclosed in, for example, U.S. Pat. No. 7,641,766, “Method of Using Aldehyde-Functionalized Polymers to Enhance Paper Machine Dewatering.”
Addition of aldehyde-functionalized polymers to the papermaking process has been conducted in many different ways to achieve the desired strength effects. Like all wet-end additives, such polymers are commonly fed directly to thin or thick stock of papermachine systems prior to the sheet forming process, but other approaches such as spraying the additive onto a wet sheet prior to the press section has also been practiced.
Sizing emulsions utilize polymers as emulsion stabilizers. Rather than being a variety of aldehyde-functionalized as described herein, these polymeric emulsion stabilizers are typically cationic vinyl addition polymers (See e.g., U.S. Pat. No. 4,657,946) and polymers and copolymers of diallyldialkylammonium halide that are substantially free of ammonium groups attached to the polymer or copolymer by only one chemical bond have also been used (e.g., U.S. Pat. No. 6,491,790). Such polymers, however, do not provide the benefits of aldehyde-functionalized polymers as discussed above.
There thus exists an ongoing industrial need in the papermaking industry to develop sizing formulations that improve sizing of paper and paperboard and also provide other enhancements to papermaking process to reduce the need for multiple chemistries.